The attainment of developmental milestones was examined and compared in 162 infants and toddlers with developmental disabilities, including Down Syndrome (n = 26), Cerebral Palsy (n = 19), Global Developmental Delay (n = 22), Premature birth (n = 66), and Seizure Disorder (n = 29). Toddlers in the Seizures Disorder group began crawling at a significantly younger age than toddlers in the Down Syndrome and Cerebral Palsy groups. Additionally, toddlers in the Seizure Disorder group began walking at a younger age than children in the Down Syndrome, Cerebral Palsy, and Global Developmental Delay groups, while toddlers in the Prematurity group began walking at a younger age than children in the Down Syndrome group. No between group differences were found with respect to age at which first words were spoken. Results and their implications are discussed. (Contains 1 table.)